Finite element modeling of electromagnetic fields and waves using NASTRAN

The various formulations of Maxwell's equations are reviewed with emphasis on those formulations which most readily form analogies with Navier's equations. Analogies involving scalar and vector potentials and electric and magnetic field components are presented. Formulations allowing for media with dielectric and conducting properties are emphasized. It is demonstrated that many problems in electromagnetism can be solved using the NASTRAN finite element code. Several fundamental problems involving time harmonic solutions of Maxwell's equations with known analytic solutions are solved using NASTRAN to demonstrate convergence and mesh requirements. Mesh requirements are studied as a function of frequency, conductivity, and dielectric properties. Applications in both low frequency and high frequency are highlighted. The low frequency problems demonstrate the ability to solve problems involving media inhomogeneity and unbounded domains. The high frequency applications demonstrate the ability to handle problems with large boundary to wavelength ratios

Response of composite plates subjected to acoustic loading

The objectives of the project were to investigate numerical methodology for the determination of narrowband response in the geometrically nonlinear regime, to determine response characteristics for geometrically nonlinear plates subjected to random loading and to compare the predictions with experiments to be performed at NASA-Langley. The first two objectives were met. The response of composite plates subjected to both narrowband and broadband excitation were studied and the results are presented and discussed

Measurement and Analysis of Oxygen/Nitrogen/5A-Zeolite Adsorption Equilibria for Air Separation

Multicomponent adsorption equilibrium data are essential for the reliable design of processes and equipment for gas separation by adsorption. We discuss techniques for the measurement and analysis of multicomponent adsorption equilibrium data, and present a comprehensive set of equilibrium data for the adsorption of oxygen and nitrogen on 5A-zeolite

Stability and electronic structure of the complex K2_2PtCl6_6 structure-type hydrides

The stability and bonding of the ternary complex K$_2$PtCl$_6$ structure hydrides is discussed using first principles density functional calculations. The cohesion is dominated by ionic contributions, but ligand field effects are important, and are responsible for the 18-electron rule. Similarities to oxides are discussed in terms of the electronic structure. However, phonon calculations for Sr$_2$RuH$_6$ also show differences, particularly in the polarizability of the RuH$_6$ octahedra. Nevertheless, the yet to be made compounds Pb$_2$RuH$_6$ and Be$_2$FeH$_6$ are possible ferroelectrics. The electronic structure and magnetic properties of the decomposition product, FeBe$_2$ are reported. Implications of the results for H storage are discussed

Metal Reduction at Cold Temperatures by Shewanella Isolates from Various Marine Environments

Members of the genus Shewanella capable of reducing metals and forming minerals under cold-temperature conditions were isolated from 3 distinct marine habitats (the coast of Wash- ington State, the Puget Sound, and an iron-rich microbial mat off Hawaii). Cultures of microorgan- isms were isolated at 8°C on nutrient agar medium prepared in artificial seawater. Isolates in this study could use a wide variety of electron acceptors such as oxygen, nitrate, and metals, and reduce various metals coupled to the oxidation of several organic acids, glucose or hydrogen at temperatures down to 0°C. Akaganeite was reduced to either magnetite or siderite, depending on the test condi- tions. The geochemical profiles at the sample sites from which these strains were isolated spanned a temperature range of 1.8 to 11°C, and all showed active oxygen and nitrate reduction as well as metal reduction. This confirms previous reports that sediment microorganisms participating in biogeo- chemical cycles remain active at low temperatures